The present invention relates to a portable electric router having a guide plate that slides over the surface of a workpiece.
An example of a conventional portable electric router is shown in FIG. 1. A housing 1 is provided for protecting and supporting within it a motor (not shown). The motor has a motor shaft (not shown) to which a rotary cutting bit (not shown) is fixed in place by means of a collet chuck 5. Further, a base 2 is provided for adjustably fixing the vertical position of the housing 1. A generally D-shaped handle 3 is fixed to one side of the base 2 by screws 16. A guide plate 4 is provided below the base 2 for slidingly moving the thus constructed router over a workpiece surface (not shown).
Such a conventional portable electric router is easy to handle because the handle 3 extends in collinear relation to the traveling direction of the rotary cutting bit. For this reason such portable electric routers can be operated with one hand. However, in such conventional portable router, it would be rather difficult to firmly depress the guide plate 4 onto the workpiece surface in intimate surface to surface contact relation due to the single-handed operation in comparison with other woodworking tools such as a portable electric circular saw shown in FIG. 3.
FIG. 4 shows the process involved when the portable electric circular saw shown in FIG. 3 cuts into a workpiece 8. A circular blade 7 rotates in a direction indicated by an arrow B. In this cutting, the workpiece 8 is urged toward a guide plate 4 because of a reaction force produced by virtue of the cutting operation. Therefore, cutting can be stably performed regardless of the size of surface area at which the guide plate 4 contacts the workpiece 8 and regardless of the absence or existence of the guide plate 4 beneath the handle 3.
In contrast, as is shown in FIG. 5, the rotary cutting bit 7 of the conventional portable electric routers rotates in the direction indicated by an arrow C. A reactionary force produced by the rotary cutting bit 7 cutting into the workpiece 8 must be overcome by contact resistance between the workpiece 8 and the guide plate 4 and by an operator's hand forcing the router toward the workpiece 8, since the workpiece is normally held immovable. Therefore, the size of surface area where the guide plate 4 contacts the workpiece 8 is extremely important to the stable operation of portable electric routers.
Ensuring proper contact of the guide plate 4 with the workpiece 8 necessitates applying downward pressure to the handle 3. However, as is shown in FIG. 1, with the conventional portable routers, a distance L separates the handle 3 from the workpiece 8. Pressing downward on the handle 3 to facilitate intimate contact of the guide plate 4 with the workpiece 8 sometimes causes the handle 3 to move downward in a direction A. As the handle 3 moves downward, the rotary cutting bit 7 rises, sometimes causing unintentional routing of a surface of the workpiece 8 as it rises. Such unintentional routing can damage or ruin the workpiece 8 which may be made from expensive materials. This problem has been especially frequent in routing of narrow width workpiece 8 such as shown in FIG. 6.
To solve this problem there is known a portable electric router as shown in FIG. 2 having an extra wide guide plate 4. Although the extra width of the guide plate 4 provides greater surface area at which the guide plate 4 contacts the workpiece 8, thereby increasing stability of the portable electric router, a new problem has been observed wherein the extra width frustrates routing in areas such as room corners wherein space for maneuvering the portable electric router is limited.